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1

Scale effects in cavitation experiments with marine propeller models

100%
Szantyr J. A.
Polish Maritime Research
|
2006
|
tom 13
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nr 4
The paper presents an overview of specificscaleeffectsencounteredinthecavitationexperi-ments with marine propeller models. These scale effects result from unavoidable dissimilarity between model and full scale flow phenomena. They may influence first of all inceptionof different forms of cavitation, but they also are visible in development and desinence of cavitation on propeller blades. These scale effects may be divided into fivemaincategories,which are described in detail. The influence of these five categories of scale effects on thedifferent aspects of cavitation performance of marine propellers is discussed
2

Dynamic interaction of the cavitating propeller tip vortex with the rudder

100%
Szantyr J. A.
Polish Maritime Research
|
2007
|
tom 14
|
nr 4
The hydrodynamic interaction between the ship propeller and the rudder has many aspects. One of the most interesting is the interaction between the cavitating tip vortex shed from the propeller blades and the rudder. This interaction leads to strongly dynamic behaviour of the cavitating vortex, which in turn generates unusually high pressure pulses in its vicinity. Possibly accurate prediction of these pulses is one of the most important problems in the hydrodynamic design of a new ship. The paper presents a relatively simple computational model of the propeller cavitating tip vortex behaviour close to the rudder leading edge. The model is based on the traditional Rankine vortex and on the potential solution of the dynamics of the cylindrical sections of the cavitating kernel passing through the strongly variable pressure field inthe vicinity of the rudder leading edge. The model reproduces numerically the experimentally observed process of initial compression of the vortex kernel in the high pressure region near the stagnation point at the rudder leading edge and subsequent explosive growth of the kernel in the low pressure region further downstream. Numerical simulation of this process enables computation of the additional pressure pulses generated due to this phenomenon and transmitted onto the hull surface. This new numerical model of the cavitating tip vortex is incorporated in the modified unsteady lifting surface program for predictionof propeller cavitation, which has been successfully used in the process of propeller design for several years and which recently has been extended to include the effects of propeller – rudder interaction. The results of calculations are compared with the experimental measurements and they demonstrate reasonable agreement between theory and physical reality
3

Experimental measurements of the hydrodynamic characteristics of the pod propulsor models

100%
Szantyr J. A.
Polish Maritime Research
|
2001
|
tom 08
|
nr 4
4

Comparative analysis of the theoretical models of ideal propulsor, ideal fluid brake, ideal screw propeller and ideal axial wind turbine

63%
Koronowicz T., Szantyr J. A.
Polish Maritime Research
|
2013
|
tom 20
|
nr 2
The article presents a detailed discussion of the theoretical models of four different fluid dynamic devices: an ideal propulsor, an ideal fluid brake, an ideal screw propeller and an ideal turbine. The four models are presented with all relevant mathematical formulae regarding the forces, the power and the efficiency. It is demonstrated that the application of the model of an ideal optimum fluid brake according to the Betz theorem for determination of the maximum effectiveness coefficient of an axial wind turbine is not correct. In the case of a turbine the inclusion of important rotational flow losses may increase the maximum value of the turbine effectiveness coefficient above the level defined by Betz. Therefore the model of an ideal turbine should be an inversion of the model of an ideal screw propeller. This conclusion is supported by numerical calculations. It may influence the design procedures of wind turbines and may lead to increase in their efficiency
5

Numerical analysis of the unsteady propeller performance in the ship wake modified by different wake improvement devices

63%
Bugalski T., Szantyr J. A.
Polish Maritime Research
|
2014
|
tom 21
|
nr 3
The paper presents the summary of results of the numerical analysis of the unsteady propeller performance in the non-uniform ship wake modified by the different wake improvement devices. This analysis is performed using the lifting surface program DUNCAN for unsteady propeller analysis. The object of the analysis is a 7000 ton chemical tanker, for which four different types of the wake improvement devices have been designed: two vortex generators, a pre-swirl stator, and a boundary layer alignment device. These produced five different cases of the ship wake structure: the original hull and hull equipped alternatively with four wake improvement devices. Two different propellers were analyzed in these five wake fields, one being the original reference propeller P0 and the other - a specially designed, optimized propeller P3. The analyzed parameters were the pictures of unsteady cavitation on propeller blades, harmonics of pressure pulses generated by the cavitating propellers in the selected points and the fluctuating bearing forces on the propeller shaft. Some of the calculated cavitation phenomena were confronted with the experimental. The objective of the calculations was to demonstrate the differences in the calculated unsteady propeller performance resulting from the application of different wake improvement devices. The analysis and discussion of the results, together with the appropriate conclusions, are included in the paper
6

A complete design of contra-rotating propellers using the new computer system

51%
Koronowicz T., Krzemianowski Z., Tuszkowska T., Szantyr J. A.
Polish Maritime Research
|
2010
|
tom 17
|
nr 1
The computer system for the complete design of the contra-rotating propellers presented in this article has several common blocks and procedures with the systems for design of single propellers and tandem co-rotating propellers, presented in detail in the Polish Maritime Research No.1 and No.4 of the Volume 16, 2009. In this article only the blocks and procedures developed specially for the contra-rotating propellers are described. The system is based on the lifting line and lifting surface models and on the Computational Fluid Mechanics methods. The comparative analysis of the contra-rotating propellers and the tandem co-rotating propellers is included
7

A complete design of ducted propellers using the new computer system

51%
Koronowicz T., Krzemianowski Z., Tuszkowska T., Szantyr J. A.
Polish Maritime Research
|
2009
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tom 16
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nr 2
The computer system for the completed design of the ducted ship propellers has some common blocks and procedures with the analogical system for open propellers that has already been presented in detail in the Polish Maritime Research [1]. This article describes only these blocks and procedures which are specific for the design of ducted propellers. These new blocks concern first of all the procedures for the design calculation of ducted propellers and for the analysis of the ducted propeller operation in the non-uniform velocity field behind the ship hull. The comparative analysis of computation results for different types of ducts is also presented
8

A complete design of tandem co-rotating propellers using the new computer system

51%
Koronowicz T., Krzemianowski Z., Tuszkowska T., Szantyr J. A.
Polish Maritime Research
|
2010
|
tom 17
|
nr 4
The computer system for the complete design of the tandem co-rotating propellers, presented in this article, has several common blocks and procedures with the computer system for the design of conventional single propellers, presented in detail in Polish Maritime Research No. 1 Vol. 16 (2009). In this article only these blocks and procedures are described, which are different in both systems. The comparative analysis of the designed tandem propeller and a conventional propeller is also included
9

Numerical prediction of steady and unsteady tip vortex cavitation on hydrofoils

51%
Flaszynski P., Szantyr J. A., Tesch K.
Polish Maritime Research
|
2012
|
tom 19
|
nr 3
The article presents the numerical method for prediction of tip vortex cavitation generated on hydrofoils. This method has been developed in the course of numerical and experimental research described in earlier publications. The objective of the research was to design the optimum discrete grid structure for this specific computational task and to select the best turbulence model for such an application The article includes a short description of the method and a computational example demonstrating its performance. In this example the results of numerical prediction of the cavitating tip vortex obtained from two commercial CFD codes are compared with experimental photographs taken in the cavitation tunnel in the corresponding flow conditions. Altogether nine different flow conditions are tested and analyzed, but only selected results are included. The accuracy of the numerical predictions is discussed and the reasons for minor existing discrepancies are identified. The unsteady tip vortex calculations are also presented, showing the fluctuations of the transverse velocity components predicted for three cross-sections of the cavitating vortex kernel
10

Critical review of propeller performance scaling methods, based on model experiments and numerical calculations

51%
Bugalski T., Streckwall H., Szantyr J. A.
Polish Maritime Research
|
2013
|
tom 20
|
nr 4
The article presents the results of experimental and numerical investigation of propeller scale effects, undertaken in co-operation of the Hamburg Ship Model Basin (HSVA), Germany, and Ship Design and Research Centre (CTO SA), Poland. The objective of the investigation was to test the adequacy of the methods currently used to account for the propeller scale effect and to develop possible improvement of the methods. HSVA has conducted model experiments in the large cavitation tunnel together with panel method and CFD calculations. CTO SA has performed model experiments in the towing tank, together with lifting surface and CFD calculations. Both institutions have suggested different new approaches to the problem and different new procedures to account for the propeller scale effects. In the article the procedures are presented together with the description of the underlying experimental and theoretical research
11

A complete design of ship propellers using the new computer system

51%
Koronowicz T., Krzemianowski Z., Tuszkowska T., Szantyr J. A.
Polish Maritime Research
|
2009
|
tom 16
|
nr 1
The computer system presented in this article is composed of several program blocks for the complete design of ship propellers. The design calculations are based on a combination of the modified lifting line theory and on the vortex lifting surface theory. The system enables solution of the following design problems:- calculation of the scale effect on the ship wake velocity field, including the influence of the propeller and rudder on this field at the propeller location- maximization of the propulsive efficiency- optimization of the propeller blade geometry on the basis of the compromise between the cavitation and blade strength requirements- optimization of the number of propeller blades and blade geometry on the basis of the acceptable levelof induced pressure pulses and unsteady shaft bearing forces- calculation of the blade spindle torque for the controllable pitch propellers.The computer system is equipped with many numerical options for graphical visualization of the input data, including an easy possibility of their correction and control of the intermediate and final results of calculations
12

A method for the accurate numerical prediction of the tip vortices shed from hydrofoils

45%
Flaszynski P., Szantyr J. A., Biernacki R., Dymarski P., Kraskowski M.
Polish Maritime Research
|
2010
|
tom 17
|
nr 2
The possibly accurate numerical prediction of the detailed structure of vortices shed from the tips of hydrofoils is an important element of the design process of marine propellers. The concentrated tip vortices are responsible for the propeller cavitation erosion and acoustic emission. The purpose of the project described in this paper was to develop the numerical method for prediction of the tip vortex structure. In the course of the project the numerical calculations were confronted with the results of experimental measurements. This led to creation of the specific method of construction of the computational grid and to selection of the optimum turbulence model. As a result the reliable method for the accurate numerical prediction of the concentrated tip vortices for different hydrofoil geometry and flow conditions has been developed and validated. This method enables elimination of the unfavourable phenomena related to the tip vortices in the course of the propeller design calculations
13

An experimental and numerical study of the vortices generated by hydrofoils

45%
Szantyr J. A., Biernacki R., Flaszynski P., Dymarski P., Kraskowski M.
Polish Maritime Research
|
2009
|
tom 16
|
nr 3
The article presents the results of the research project concerning the process of formation of the tip vortices shed from hydrofoils of different geometry in different flow conditions. Three hydrofoils resembling the contemporary marine propeller blades have been selected for the study. The experimental part of the project consisted of the LDA measurements of the velocity field in three cross-sections of the vortex generated by the hydrofoils in the cavitation tunnel. The numerical part of the project consisted of calculations of the corresponding velocity field by means of three computer codes and several selected turbulence models. The comparative analysis of the experimental and numerical results, leading to the assessment of the accuracy of the numerical methods, is included
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